not much

test/test_mesh3D.py

@@ -24,6 +24,12 @@ class Sphere_Test(Tensors_Check, unittest.TestCase):
         x, y, z = sympy.symbols('x y z')
         self._inst.cut(x + 1./100*y > 0, at_intersection='split')
 
+    def test_triangle(self):
+        tri = self._inst.triangles()
+        mesh = tri.mesh()
+        print(self._inst, mesh)
+        self.assertTrue(self._inst.equal(mesh))
+
 
 class IO_Stl_test(unittest.TestCase):
     def setUp(self):

tfields/core.py

@@ -1406,6 +1406,26 @@ class Tensors(AbstractNdarray):
         return inst, template
 
     def _cut_template(self, template):
+        # # Redirect fields
+        # fields = []
+        # if template.fields:
+        #     template_field = np.array(template.fields[0])
+        #     if len(self) > 0:
+        #         '''
+        #         if new vertices have been created in the template, it is
+        #         in principle unclear what fields we have to refer to.
+        #         Thus in creating the template, we gave np.nan.
+        #         To make it fast, we replace nan with 0 as a dummy and correct
+        #         the field entries afterwards with np.nan.
+        #         '''
+        #         nan_mask = np.isnan(template_field)
+        #         template_field[nan_mask] = 0  # dummy reference to index 0.
+        #         template_field = template_field.astype(int)
+        #         for field in self.fields:
+        #             projected_field = field[template_field]
+        #             projected_field[nan_mask] = np.nan  # correction for nan
+        #             fields.append(projected_field)
+        # return type(self)(Tensors(template), *fields)
         return self[template.fields[0]]
 
     def cut(self, expression, coord_sys=None, return_template=False, **kwargs):
@@ -2389,7 +2409,52 @@ class TensorMaps(TensorFields):
         return inst, template
 
     def _cut_template(self, template):
+        """
+        Args:
+            template (tfields.TensorMaps)
+
+        Examples:
+            >>> import tfields
+            >>> import numpy as np
+
+            Build mesh
+            >>> mmap = tfields.TensorFields([[0, 1, 2], [0, 3, 4]],
+            ...                             [[42, 21], [-42, -21]])
+            >>> m = tfields.Mesh3D([[0]*3, [1]*3, [2]*3, [3]*3, [4]*3],
+            ...                    [0.0, 0.1, 0.2, 0.3, 0.4],
+            ...                    [0.0, -0.1, -0.2, -0.3, -0.4],
+            ...                    maps=[mmap])
+
+            Build template
+            >>> tmap = tfields.TensorFields([[0, 3, 4], [0, 1, 2]],
+            ...                             [1, 0])
+            >>> t = tfields.Mesh3D([[0]*3, [-1]*3, [-2]*3, [-3]*3, [-4]*3],
+            ...                    [1, 0, 3, 2, 4],
+            ...                    maps=[tmap])
+
+            Use template as instruction to make a fast cut
+            >>> res = m._cut_template(t)
+            >>> assert np.array_equal(res.fields,
+            ...                       [[0.1, 0.0, 0.3, 0.2, 0.4],
+            ...                        [-0.1, 0.0, -0.3, -0.2, -0.4]])
+
+            >>> assert np.array_equal(res.maps[3].fields[0],
+            ...                       [[-42, -21], [42, 21]])
+
+        """
         inst = super()._cut_template(template)
+        # # Redirect maps and their fields
+        # maps = []
+        # for mp, template_mp in zip(self.maps.values(), template.maps.values()):
+        #     mp_fields = []
+        #     for field in mp.fields:
+        #         if len(template_mp) == 0 and len(template_mp.fields) == 0:
+        #             mp_fields.append(field[0:0])  # np.empty
+        #         else:
+        #             mp_fields.append(field[template_mp.fields[0].astype(int)])
+        #     new_mp = tfields.TensorFields(tfields.Tensors(template_mp),
+        #                                   *mp_fields)
+        #     maps.append(new_mp)
 
         if template.fields:
             # bulk was cut so we need to correct the map references.